Polyurethane Sealant Based on Poly(Butylene Oxide) Polyols for Glass Sealing

ABSTRACT

A polyurethane glass sealant is made by reacting a poly(1,2-butylene oxide) polymer with a chain extender and a polyisocyanate. The poly(1,2-butylene oxide) polymer may be used as a mixture with up to 50% by weight of other polyols, including castor oil. The sealant is especially useful as a secondary sealant for an insulated glass unit (IGU).

This invention relates to a polyurethane sealant for glass sealing, to amethod of sealing glass surfaces, to a method for making insulated glassunits and to insulated glass units sealed with a polyurethane sealant.

Sealants are often applied to glass windows to bond the glass to a frameor other substrate and prevent gas and water leakage around the edges.An example of this is automotive windshields. In addition, many buildingglazing applications rely on a sealant to bond the glass to the framestructure. The general requirements for these materials are that they beelastomeric and that they bond well to glass and other materials. Inaddition, they need to form good barriers against the penetration ofgases and liquids. To accomplish this, the sealant materials need toprevent leakage at the interface between the sealant and the substrates,as well as through the sealant material itself.

A glazing application of commercial significance is insulating glassunits (IGUs). IGUs generally comprise two or more parallel glass panesheld a small distance apart by a spacer. The space enclosed between thepanes typically holds a vacuum or is filled with air or an inert gassuch as argon, helium or xenon. The vacuum or trapped inert gascontributes much of the thermal insulation properties of these IGUs.Sealants hold the unit together and provide a barrier to the passage ofgas into and out of the enclosed space between the panes. This isimportant to maintain the thermal insulation properties of the units. Inaddition, the sealants prevent water from permeating into the unit. Thishelps to prevent fogging.

IGUs typically make use of two different sealant materials. A “primary”sealant is used to seal the glass panes directly to a spacer, which asits name implies defines the spacing between adjacent glass panes andtherefore the thickness of the enclosed vacuum or gas space. Thematerial of choice as the primary sealant is polyisobutylene, which isan excellent barrier to both moisture and gasses. However,polyisobutylene does not provide the mechanical properties and adhesivestrength that are needed. Therefore, it is typical to manufacture theIGU using a secondary sealant. This secondary sealant provides thenecessary adhesion and mechanical strength, but also is important inpreventing the passage of moisture and gas into and out of the unit,especially if the primary sealant becomes damaged or degraded over time.

The highest-performing polyurethane secondary sealant currently used inIGU is based on a polybutadiene polyol. These polyurethanes haveexcellent moisture vapor permeation rates but suffer from inadequate UVstability. Because of the poor UV stability, these polyurethane sealantsdegrade over time, and the life of the IGU is shortened. Thesepolyurethanes are also susceptible to hydrolytic instability.

Other polyurethane secondary sealants have performed even less well.Those based on polymers of propylene oxide suffer from highpermeabilities to both moisture vapor and gases. They also show poor UVstability and sometimes inadequate hydrolytic stability, and IGUscontaining them have short lifetimes.

Low water permeability often does not correlate to low gas permeabilityin substantially non-cellular polymers. That is because low waterpermeability is favored by a high level of hydrophobicity in the sealantpolymer, and increasing hydrophobicity tends to favor permeation byatmospheric gases and non-polar gases such as argon that is commonlyused to fill the space between the glass panes of an IGU. Therefore,measures that tend to decrease water permeability often are seen to havean adverse impact on gas permeability, and vice versa.

Still another drawback of the polyurethanes is that large quantities ofa plasticizer compound often must be included in the formulation forprocessing reasons. The polyurethane is typically made by mixing apolyol component with a polyisocyanate compound. The significantdifferences in the viscosities between these components can lead todifficulties in mixing; thereby requiring longer mixing times. Due tothe reactive nature of the components used, there are processingdrawbacks related to viscosity increase and exotherm. The plasticizer isincluded to reduce the viscosity of the polyol component to facilitatemixing, to ameliorate the viscosity increase during early stages of cureand to reduce the exotherm by acting as a heat sink. For these reasons,the plasticizer is widely understood to be necessary to process thepolyurethane system with the equipment used in the industry. Over time,this plasticizer can leach into the space between the glass panes andcause fogging. This potential for fogging can be ameliorated by reducingthe plasticizer level or eliminating it completely.

Therefore, it would be desirable to provide a thermosetting, elastomericsealant for glass installations, which sealant has good processingcharacteristics, exhibits good adhesion to glass, provides the neededbarrier to gasses and liquids (including atmospheric moisture) and hasthe necessary physical properties, UV stability and hydrolyticstability.

This invention is in one aspect a process for forming a seal betweenglass and a substrate, comprising:

a) forming a curable reaction mixture by combining ingredientsincluding 1) a poly(1,2-butylene oxide) polyol having a hydroxylequivalent weight of at least 500, or a mixture of 50 to 99% by weightof a poly(1,2-butylene oxide) polyol having a hydroxyl equivalent weightof at least 500 with 1 to 50% by weight of at least one other polyolselected from (i) polymers and copolymers of propylene oxide having anequivalent weight of at least 300 and (ii) a hydroxyl-containing fat oroil, wherein component 1) has an average nominal functionality of atleast 2.2 hydroxyl groups per molecule; 2) at least one chain extenderand 3) at least one organic polyisocyanate, wherein the isocyanate indexis 70 to 130;

b) applying the curable reaction mixture to an interface between saidglass and said substrate and in contact with both said glass and saidsubstrate;

c) curing the curable reaction mixture to form an elastomeric sealbetween the glass and the substrate.

In specific embodiments, the invention is a process for producing anedge seal for a multi-pane glass assembly, wherein the multi-pane glassassembly comprises at least one pair of substantially parallel glasssheets, the glass sheets of said pair being separated from each other byone or more spacers positioned between the pair of glass sheets and ator near at least one edge of the glass sheets; the process comprising

a) applying a curable reaction mixture to said at least one edge of thepair of glass sheets and into contact with each of the pair of glasssheets and the spacer(s) separating said pair of glass sheets and

b) curing the curable reaction mixture to form an elastomeric edge sealbetween the pair of glass sheets and adherent to the spacer(s)separating the pair of glass sheets; wherein the curable reactionmixture contains 1) a poly(1,2-butylene oxide) polyol having a hydroxylequivalent weight of at least 500, or a mixture of 50 to 99% by weightof a poly(1,2-butylene oxide) polyol having a hydroxyl equivalent weightof at least 500 with 1 to 50% by weight of at least one other polyolselected from (i) polymers and copolymers of propylene oxide having ahydroxyl equivalent weight of at least 300 and (ii) ahydroxyl-containing fat or oil, wherein component 1) has an averagenominal functionality of at least 2.2 hydroxyl groups per molecule; 2)at least one chain extender and 3) at least one organic polyisocyanate,and wherein the isocyanate index is 70 to 130.

The invention is also a multi-pane glass assembly comprising at leastone pair of substantially parallel glass sheets, the glass sheets ofsaid pair being separated from each other by one or more spacerspositioned between the pair of glass sheets at or near at least one edgeof the glass sheets, and an elastomeric edge seal bonded to said edge ofthe glass sheets and the spacer(s), wherein the elastomeric edge seal isa polymer formed by curing a curable reaction mixture formed bycombining ingredients including 1) a poly(1,2-butylene oxide) polyolhaving a hydroxyl equivalent weight of at least 500, or a mixture of 50to 99% by weight of a poly(1,2-butylene oxide) polyol having a hydroxylequivalent weight of at least 500 with 1 to 50% by weight of at leastone other polyol selected from (i) polymers and copolymers of propyleneoxide having a hydroxyl equivalent weight of at least 300 and (ii) ahydroxyl-containing fat or oil, wherein component 1) has an averagenominal functionality of at least 2.2 hydroxyl groups per molecule; 2)at least one chain extender and 3) at least one organic polyisocyanate,wherein the isocyanate index is 70 to 130.

This invention provides a readily-processable, thermosetting,elastomeric sealant for glass installations. The sealant compositiondoes not require the presence of thiram or manganese dioxide, whichpreferably are absent from the composition. The cured sealant forms astrong elastomeric seal between glass and a substrate material, withgood adhesion and low permeability to gases and liquids.

The FIGURE is a side view of a multipane glass assembly sealed with anelastomeric seal, in accordance with the invention.

In this invention, a seal is formed between glass and a substrate. By“glass”, it is meant any inorganic amorphous material having a glasstransition temperature of at least 100° C. It preferably is transparentto visible light. A preferred type of glass is a silica glass, by whichis meant a glass containing 50% or more by weight silica. Among thesilica glasses are fused silica glass, soda-lime-silica glass, sodiumborosilicate glass, lead oxide glass, aluminosilicate glass and thelike. Another preferred type of glass is so-called “oxide glass”, whichcontains alumina and a minor amount of germanium oxide.

The glass may have one or more coatings on either or both of its mainsurfaces. Examples of such coatings include reflective coatings ofvarious types, such as IR, UV or visible light reflective surfaces, IRabsorbers, UV absorbers, tints or other coloring layers, and the like.

The glass may have a multi-layer construction. For example, the glassmay consist of two or more glass layers bonded by one or moreintermediate layers of an adhesive polymer.

The substrate can be any solid material, including, for example, ametal, a ceramic, another glass, an organic polymer, a lignocellulosicmaterial such as wood, paper, cotton and the like or another biologicalor natural material. An organic polymer may be, for example, a syntheticor biological-origin polymer, and may be a thermoplastic or a thermoset.

In specific embodiments, the glass forms a window for a vehicle,building or other construction and the substrate is a frame element towhich the window is affixed. The frame element may be a vehicle framestructure (or a part thereof). The frame element may be a window sash,door stile or other structural support to which the window is affixed.

In other specific embodiments, the substrate is a spacer for amulti-pane glass assembly such as an insulating glass unit (IGU). Such amulti-pane assembly comprises at least one pair of substantiallyparallel glass sheets. The glass sheets are separated from each other byone or more peripheral spacers positioned between the glass sheets at ornear at least one edge. A multi-pane assembly may contain any largernumber of substantially parallel glass sheets, with each adjacent pairbeing separated by a peripheral spacer.

A representation of a multi-pane assembly is shown in the FIGURE. In theFIGURE, substantially parallel glass panes 1 are separated by spacer 2near edge 11, defining space 4 between the two glass panes 1. As istypical, spacer 2 is recessed slightly from edge 11, leaving a cavity 8that is defined by the interior faces 10 of each of panes 1 and theexterior surface 9 of spacer 2. Spacer 2 typically is positioned alongthe substantial length of edge 11 of glass panes 1, and more typicallyspacers such as spacer 2 will be positioned about the entire peripheryof glass panes 1. Sealant 5 of this invention is bonded to said edge 11of the glass sheets 1 and to spacer 2, forming a seal between each ofglass panes 1 and spacer 2, and between glass panes 1. As shown, sealant5 occupies cavity 8 formed defined by the interior faces 10 of each ofpanes 1 and the exterior surface 9 of spacer 2.

In the particular embodiment shown in the FIGURE, spacer 2 is hollow,and is filled with optional desiccant 6. Desiccant 6 often is providedto absorb moisture from the gas contained within space 4. Space 4 istypically filled with a gas such as air, nitrogen, helium argon, xenonand the like.

Also shown in the FIGURE are primary sealants 3, which are optional butare often included in insulating glass units. Primary sealants 3 areclosest to the air gap between glass sheets 2 and are generally presentto keep moisture vapor and gasses from moving in and out of space 4.Primary sealant 3 is preferably polyisobutylene, but may be anotherpolymer having barrier properties.

Sealant 5 is a reaction product of a curable reaction mixture formed bycombining at least the following ingredients:

1) a poly(1,2-butylene oxide) polyol having a hydroxyl equivalent weightof at least 500 or a mixture of 50 to 99% by weight of apoly(1,2-butylene oxide) polyol having a hydroxyl equivalent weight ofat least 500 with 1 to 50% by weight of at least one other polyolselected from (i) polymers and copolymers of propylene oxide having ahydroxyl equivalent weight of at least 300 and (ii) ahydroxyl-containing fat or oil, wherein component 1) has an averagenominal functionality of at least 2.2 hydroxyl groups per molecule; 2)at least one chain extender and 3) at least one polyisocyanate, andwherein the isocyanate index is 70 to 130.

The poly(1,2-butylene oxide) polyol is a homopolymer of 1,2-butyleneoxide, or a copolymer thereof with up to 25%, preferably up to 10% andmore preferably up to 5%, based on the combined weight of all monomers,of a copolymerizable alkylene oxide such as, for example, ethyleneoxide, 1,2-propylene oxide, 2,3-butylene oxide, tetrahydrofuran,1,2-hexane oxide, and the like. Poly(1,2-butylene oxide) homopolymersare preferred. The poly(1,2-butylene oxide) polyol can be prepared inknown fashion by polymerizing 1,2-butylene oxide (alone or together withone or more comonomers as described) in the presence of an initiatorcompound. The polymerization is generally catalyzed, using catalystssuch as alkali metal hydroxide, double metal cyanide catalysts and thelike.

The initiator compound(s) used in the polymerization contains onaverage, at least 1.8 groups that can be alkoxylated. The nominalfunctionality of the poly(1,2-butylene oxide) polyol is equal to thenumber of alkoxylatable sites on the initiator compound or, if a mixtureof initiator compounds is used, the average number of alkoxylatablesites per molecule in the mixture. Preferred initiator compounds containtwo or more hydroxyl groups, although compounds containing aminehydrogens are also useful. The initiator compound preferably has anequivalent weight per alkoxylatable site of 15 to 150 and morepreferably 30 to 75. Examples of suitable initiator compounds includeethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, dipropylene glycol, tripropylene glycol, 1,4-butane diol,cyclohexane dimethanol, glycerin, trimethylolethane, trimethylolpropane,erythritol, pentaerythritol, ethylene diamine, propylene diamine,aniline, toluene diamine, and the like.

The poly(1,2-butylene oxide) polyol preferably has a nominalfunctionality of 2 to 3, more preferably 2 to 2.5, and an equivalentweight per hydroxyl group of 500 to 3000, especially 800 to 2500 andmost preferably 800 to 1500.

The poly(1,2-butylene oxide) polyol may be the only high equivalentweight (i.e., 200 g/equivalent or more) polyol in the reaction mixture,if it has a nominal functionality of at least 2.2. If thepoly(1,2-butylene oxide) polyol has a nominal functionality below 2.2,it is necessary to provide a second polyol to increase the averagenominal functionality to at least 2.2. Such a second polyol may also bepresent even if the nominal functionality of the poly(1,2-butyleneoxide) polyol is 2.2 or greater.

In some embodiments, the second polyol is a polymer or copolymer ofpropylene oxide that has a hydroxyl equivalent weight of at least 300.The propylene oxide may be 1,3-propylene oxide, but more typically is1,2-propylene oxide. If a copolymer, the comonomer is anothercopolymerizable alkylene oxide such as, for example, ethylene oxide,2,3-butylene oxide, tetrahydrofuran, 1,2-hexane oxide, and the like. Acopolymer may contain 75% or more by weight, preferably 85% or morepolymerized propylene oxide, based on the total weight of polymerizedalkylene oxides. A copolymer preferably contains no more than 15%,especially no more than 5% by weight polymerized ethylene oxide. Thepolymer or copolymer of propylene oxide should have a nominalfunctionality of at least 2.0. The nominal functionality preferably is2.5 to 6, more preferably 2.5 to 4 or 2.5 to 3. The hydroxyl equivalentweight of the polymer or copolymer of propylene oxide is at least 300,preferably at least 500, more preferably 500 to 3000, in someembodiments 800 to 2500 and in particular embodiments from 800 to 1500.

The polymer or copolymer of propylene oxide can be made in the samegeneral manner as described with respect to the 1,2-butylene oxidepolymer, except for the selection of monomers. Suitable initiatorcompounds to produce the polymer or copolymer of propylene oxide includethose described above with respect to the 1,2-butylene oxide polymer.

In other embodiments, the second polyol is a hydroxyl-containing fat oroil. The hydroxyl-containing fat or oil should contain an average of atleast two, preferably at least 2.2 hydroxyl groups per molecule.Suitable such oils include naturally-occurring plant oils such as castoroil and lesquerella oil. Castor oil is a preferred hydroxyl-containingoil.

Mixtures of two or more of the foregoing second polyols can be present.

When a mixture of polyols is used, the poly(1,2-butylene oxide)constitutes 50 to 99% by weight of the mixture, and the second polyol(s)constitutes 1 to 50% thereof. The poly(1,2-butylene oxide) preferablyconstitutes 70 to 99% by weight of the mixture, and more preferably 70to 90% by weight of the mixture, with the second polyol(s)correspondingly constituting the remainder of the weight of the mixture.

Component 1) has an average nominal hydroxyl functionality of at least2.2, and preferably at least 2.3. Its average nominal hydroxylfunctionality may be as high as six, but preferably is up to 4 and morepreferably up to 3. The average hydroxyl equivalent weight ofcomponent 1) may be from about 500 to 3000, and is more preferably 500to 1500 and still more preferably from 600 to 1200.

Especially preferred as Component 1) is a mixture of 70 to 95% by weightof a poly(1,2-butylene oxide) polymer as described before and 5 to 30%by weight of castor oil. Such especially preferred mixtures may contain85 to 95% by weight of the poly(1,2-butylene oxide) and 5 to 15% byweight of castor oil. In these especially preferred embodiments, thepoly(1,2-butylene oxide) polyol preferably has a nominal functionalityof 2 to 3, more preferably 2 to 2.5, and an equivalent weight perhydroxyl group of 500 to 3000, especially 800 to 2500 and mostpreferably 800 to 1500.

Component 2) is a chain extender, by which is meant a compound havingexactly two isocyanate-reactive groups and a weight perisocyanate-reactive group of up to 300, preferably 30 to 150, and morepreferably 30 to 75. The isocyanate-reactive groups may be, for example,hydroxyl, primary amino or secondary amino groups. Hydroxyl groups aregenerally preferred. Examples of hydroxyl-containing chain extenders areethylene glycol, 1,2-propane diol, 1,3-propane diol, 1,4-butane diol,2,2,4-trimethylpentane-1,3-diol, 2-ethylhexane diol,N,N-bis(2-hydroxylpropyl)aniline, diethylene glycol, triethylene glycol,dipropylene glycol, tripropylene glycol, cyclomethanedimethanol, and thelike. Among these, the linear, acyclic, hydroxyl chain extenders aregenerally preferred, and α,ω-alkylene glycols and α,ω-polyalkyleneglycols such as ethylene glycol, 1,4-butane diol, 1,3-propane diol,diethylene glycol, triethylene glycol and the like are especiallypreferred.

The organic polyisocyanate advantageously contains an average of atleast 2.0 isocyanate groups per molecule. A preferred isocyanatefunctionality is from about 2.0 to about 3.0 or from about 2.0 to about2.5 isocyanate groups per molecule. The polyisocyanate advantageouslyhas an isocyanate equivalent weight of 75 to 200. This is preferablyfrom 80 to 170.

Suitable polyisocyanates include aromatic, aliphatic and cycloaliphaticpolyisocyanates. Exemplary polyisocyanates include, for example,m-phenylene diisocyanate, 2,4- and/or 2,6-toluene diisocyanate (TDI),the various isomers of diphenylmethanediisocyanate (MDI),hexamethylene-1,6-diisocyanate, tetramethylene-1,4-diisocyanate,cyclohexane-1,4-diisocyanate, hexahydrotoluene diisocyanate,hydrogenated MDI (H₁₂ MDI), naphthylene-1,5-diisocyanate,methoxyphenyl-2,4-diisocyanate, 4,4′-biphenylene diisocyanate,3,3′-dimethyoxy-4,4′-biphenyl diisocyanate,3,3′-dimethyldiphenylmethane-4,4′-diisocyanate, 4,4′,4″-triphenylmethanediisocyanate, polymethylene polyphenylisocyanates, hydrogenatedpolymethylene polyphenyl polyisocyanates, toluene-2,4,6-triisocyanateand 4,4′-dimethyldiphenylmethane-2,2′,5,5′-tetraisocyanate. Any of theforegoing polyisocyanates may be modified to include urea, isocyanurate,uretidinedione, allophonate, biuret, carbodiimide, urethane or otherlinkages.

Among the preferred polyisocyanates are MDI, “liquid MDI” products inwhich MDI is modified to contain urea, uretonimine, allophonate, biuret,carbodiimide and/or urethane linkages to produce a material having amelting temperature below 20° C. and an isocyanate equivalent weight of135 to 170, and the so-called polymeric MDI products, which are amixture of polymethylene polyphenylene polyisocyanates in monomeric MDI.

The polyisocyanate is used in an amount sufficient to provide anisocyanate index of 70 to 130. Isocyanate index is calculated as thenumber of reactive isocyanate groups provided to the reaction mixturedivided by the number of isocyanate-reactive groups provided to thereactive mixture, and multiplying by 100. A preferred isocyanate indexis 90 to 125 and a more preferred isocyanate index is 95 to 115.

In addition, the amounts of polyisocyanate and chain extender (and anycrosslinkers as may be present) are chosen together such that thepolyurethane has a hard segment content of 10 to 50%, preferably 15 to35% and more preferably 18 to 30% by weight. Hard segment content iscalculated by dividing the combined weight of polyisocyanate(s), chainextender(s) and crosslinker(s) (if any) by the total weight of allpolyisocyanate(s) and isocyanate-reactive materials (other than reactivecatalysts, if any) provided to the reaction mixture.

The curable reaction mixture may contain other ingredients in additionto those already described. Among these are, for example, catalysts,plasticizers, crosslinkers, UV stabilizers, biocides, preservatives,adhesion promoters, colorants, fillers, desiccants and water scavengers,and the like.

Examples of catalysts include tertiary amines, tin carboxylates;organotin compounds; tertiary phosphines; various metal chelates; metalsalts of strong acids, such as ferric chloride, stannic chloride,stannous chloride, antimony trichloride, bismuth nitrate and bismuthchloride, and the like. Tertiary amine and tin catalysts are generallypreferred.

Representative tertiary amine catalysts include trimethylamine,triethylamine, N-methylmorpholine, N-ethylmorpholine,N,N-dimethylbenzylamine, N,N-dimethylethanolamine,N,N,N′,N′-tetramethyl-1,4-butanediamine, N,N-dimethylpiperazine,1,4-diazobicyclo-2,2,2-octane, bis(dimethylaminoethyl)ether,bis(2-dimethylaminoethyl) ether, morpholine,4,4′-(oxydi-2,1-ethanediyl)bis, triethylenediamine, pentamethyldiethylene triamine, dimethyl cyclohexyl amine, N-cetyl N,N-dimethylamine, N-coco-morpholine, N,N-dimethyl aminomethyl N-methyl ethanolamine, N,N,N′-trimethyl-N′-hydroxyethyl bis(aminoethyl) ether,N,N-bis(3-dimethylaminopropyl)N-isopropanolamine, (N,N-dimethyl)amino-ethoxy ethanol, N,N, N′,N′-tetramethyl hexane diamine,1,8-diazabicyclo-5,4,0-undecene-7, N,N-dimorpholinodiethyl ether,N-methyl imidazole, dimethyl aminopropyl dipropanolamine,bis(dimethylaminopropyl)amino-2-propanol, tetramethylamino bis(propylamine), (dimethyl(aminoethoxyethyl))((dimethyl amine)ethyl)ether,tris(dimethylamino propyl) amine, dicyclohexyl methyl amine,bis(N,N-dimethyl-3-aminopropyl) amine, 1,2-ethylene piperidine andmethyl-hydroxyethyl piperazine.

Examples of useful tin-containing catalysts include stannous octoate,dibutyl tin diacetate, dibutyl tin dilaurate, dibutyl tin dimercaptide,dialkyl tin dialkylmercapto acids, dibutyl tin oxide, dimethyl tindimercaptide, dimethyl tin diisooctylmercaptoacetate, and the like.

The catalysts are typically used in small amounts, such as 0.0015 to 5,preferably from 0.01 to 1 part by weight per 100 parts by weight ofpolyol(s) plus polyisocyanate(s). Tin-containing catalysts are typicallyused in amounts towards the low end of these ranges.

A plasticizer may be present. If present, the plasticizer preferably ismixed with the poly(1,2-butylene oxide) polymer to reduce its viscosityand so facilitate mixing with the polyisocyanate, which typically has amuch lower viscosity. Examples of suitable plasticizers include liquid(at 25° C.) esters of monocarboxylic acids and diesters of dicarboxylicacids having molecular weights of up to about 300. Among these are, forexample, dialkyl phthalate esters, dialkyl terephthalate esters,trialkyl trimellitates, dialkyl adipate esters, dialkyl maleate esters,dialkyl sebacate esters, alkanolic acid diesters of alkylene glycols,alkanoic acid diesters of polyalkylene glycols, and the like. Apreferred plasticizer is trimethylpentyl diisobutyrate.

The amount of plasticizer, if used, may range from 1 to 50% of thecombined weight of the plasticizer and all reactive materials(isocyanates and isocyanate reactive materials) provided to the reactionmixture. An advantage of the invention is that often only small amountsof plasticizer are needed. Therefore, a preferred amount is from 1 to20%, in some embodiments 5 to 15%, and in other embodiments 10 to 13% byweight, on the same basis as before. The use of a plasticizer tends toreduce tensile strength while increasing elongation and increasing sag.Since excessive sag can be a drawback, the ability to use small amountsof plasticizer (if any at all) can be a significant advantage of thisinvention. In addition, smaller amounts of plasticizer in the sealantreduce the risk and severity of fogging due to the leaching of theplasticizer.

Crosslinkers are for purposes of this invention compounds having atleast three isocyanate-reactive groups per molecule and an equivalentweight per isocyanate-reactive group of less than 200, preferably 30 to150. Examples of crosslinkers include glycerin, trimethylolpropane,trimethylolethane, pentaerythritol, erythritol, sorbitol, andalkoxylates of any of the foregoing having an equivalent weight of up to300. If used at all, crosslinkers are generally present in smallquantities, such as up to 5% of the weight of the curable reactionmixture.

Fillers can be present to provide desired rheological properties andreduce cost. Examples of fillers include inorganic particulate materialssuch as talc, titanium dioxide, calcium carbonate, mica, wollastonite,fly ash and the like; metal particles; carbon black; graphite; highmelting organic polymers, and the like. The particle size of thesefillers (as determined using screening methods) may be up to 50 microns,preferably 0.2 to 30 microns. Fillers may constitute up to 90% by weightof the curable reaction mixture, preferably 25 to 80% by weight.

A seal is formed in accordance with the invention by forming a curablereaction mixture, applying it to an interface between and in contactwith said glass and said substrate and then curing the curable reactionmixture to form an elastomeric seal between the glass and the substrate.

The reaction mixture is formed by mixing the foregoing necessary andoptional (if any) components. It is generally preferred to formulate thestarting ingredients into two components. The first component includesthe isocyanate-reactive components, including component 1), the chainextender (component 2) and any crosslinker. The second componentincludes the polyisocyanate compound(s). The catalyst(s) can beformulated into either or both of these components, but preferably areformulated into the first component. The plasticizer if any ispreferably incorporated into the first component.

Mixing and application can be done in any convenient manner. In thepreferred case in which the ingredients are formulated into twocomponents, the components are simply combined at ambient temperature orany desirable elevated temperature, deposited onto the interface betweenglass and substrate, and allowed to react. The mixing of the componentscan be done in any convenient way, depending on the particularapplication and available equipment. Mixing of the components can bedone batchwise, mixing them by hand or by using various kinds of batchmixing devices, followed by application by brushing, pouring, applying abead and/or in other suitable manner. The two components can be packagedinto separate cartridges and simultaneously dispensed through a staticmixing device to mix and apply them, typically as a bead, onto theinterface.

Spraying methods are also useful. In a spraying method, the individualingredients or formulated components are brought under pressure to amixhead, where they are combined and dispensed under pressure to theinterface between glass and substrate.

Other continuous metering and dispensing systems also are useful to mixand dispense the reaction mixture and apply it to the interface betweenglass and substrate.

Curing in many cases proceeds spontaneously at room temperature (about20° C.), and in such cases can be effected without application of heat.The curing reaction is generally exothermic, and a correspondingtemperature rise may occur.

A faster and/or more complete cure often is seen at higher temperatures,and for that reason it may be desirable in some embodiments to applyheat to the applied reaction mixture. Therefore, a wide range of curingtemperatures can be used, such as, for example, a temperature from 0 to180° C. A more typical range is from 4 to 120° C., and a preferred rangeis 10 to 80° C. This can be done, for example, by (a) heating one ormore of the starting materials prior to mixing it with the others toform the reaction mixture and/or (b) heating the reaction mixture afterit has been formed by combining the raw materials.

Multi-pane glass assemblies made in accordance with the invention areuseful as insulating glass units, as solar modules, and the like.

The following examples are provided to illustrate the invention, but notlimit the scope thereof. All parts and percentages are by weight unlessotherwise indicated.

EXAMPLES 1-4

Example 1 is prepared as follows: A polyol blend is prepared by mixing50 parts of a 2000 molecular weight difunctional poly(1,2-butyleneoxide) homopolymer, and 50 parts a 3000 molecular weight nominallytrifunctional poly(1,2-propylene oxide) homopolymer. To this blend areadded 4.5 parts 1,4-butanediol and about 0.04 parts of a tin catalyst.This blend is mixed with a 143 isocyanate equivalent weight “liquid” MDIproduct at an isocyanate index of 1.02 to form a reaction mixture. Theresulting cured elastomer contains 25.2% hard segment. The reactionmixture is compression molded at 50° C. for 30 minutes under an appliedpressure of 20,000 psi (about 140 MPa) for 30 minutes. Tensile strengthand elongation are measured according to ASTM 1708, and are as reportedin Table 1 below. Results are as indicated in Table 1.

Examples 2-6 are made in the same manner, except in each case the1,4-butanediol is replaced with another chain extender, as indicated inTable 1. The amount of chain extender and the hard segment content ofthe elastomers are as indicated in Table 1. For Examples 3-6, the ShoreA hardness is measured according to ASTM D2240.

TABLE 1 Example Chain Extender, Hard Segment Tensile Strength, Shore ANo. amount (parts) Content, % MPa (psi) Elongation, % Hardness 11,4-butanediol, 4.5 25.2 4.07 (590) 324 ND 2 2,2,4-trimethylpentane-1,3-diol, 6.5 25.5 1.72 (250) 485 ND 3 2-ethyl hexane diol, 6.525.5 1.71 (248) 505 30 4 1,2-propane diol, 4 25.4 2.65 (384) 538 35 51,3-propane diol, 4 25.4 1.74 (252) 539 31 6N,N-bis(2-hydroxylpropyl)aniline, 8 25.2  340 (234) 450 40

When used to seal the edge of a multi-pane glass assembly, each ofExamples 1 through 6 demonstrates excellent adhesion to the glass andspacer, and forms a high quality seal.

EXAMPLES 7-11

Example 7 is prepared by mixing 70 parts of a 2000 molecular weightdifunctional poly(1,2-butylene oxide) homopolymer with 30 parts castoroil. To this blend are added 1.5 parts 1,4-butanediol and 0.04 parts ofa tin catalyst. The amount of 1,4-butanediol is selected so that theresulting cured elastomer contains 25% hard segment when cured at a 1.1isocyanate index. This mixture is then combined with a 143 isocyanateequivalent weight “liquid” MDI product at an isocyanate index of 1.1 toform a reaction mixture, which is cured as described with respect toExamples 1-6. Tensile strength, elongation and Shore A hardness aremeasured as before, with results as are indicated in Table 2 below.

Samples of the cured films are cut into dog-bones for evaluating theeffect of water immersion on mechanical properties. The initial weight(W₀) of the films is determined. The film is in each case then immersedfor 24 hours in DI water maintained at 25° C. or in boiling water for 1hour. After the specified time, the film is then dried with a tissue toremove surface water and weighed to obtain weight W₁. The waterabsorption is calculated using equation:

Water uptake=(W ₁ −W ₀)/W ₀)×100%

Examples 8-11 are prepared and tested in the same manner, except theratio of poly(1,2-butylene oxide) homopolymer and castor oil is variedas indicated in Table 2.

TABLE 2 Mechanical Properties Poly(BO)/ Water Tensile Ex. Castor Oiluptake, Strength, Elongation, Shore A No. Ratio¹ wt-% MPa (psi) %hardness 7 70/30 0.69 2.41 (350) 295 55 8 75/25 0.72 2.05 (297) 294 50 980/20 0.79 1.86 (270) 236 50 10 85/15 0.81 1.92 (279) 450 39 11 90/100.92 1.57 (227) 445 33 ¹The weight ratio of the poly(butylene oxide)diol and the castor oil in the formulation.

When used to seal the edge of a multi-pane glass assembly, each ofExamples 7 through 11 demonstrates excellent adhesion to the glass andspacer, and forms a high quality seal.

EXAMPLE 12

A sealant composition is made and cured in the general manner describedin the previous examples. The formulation is 85 parts of a 2000molecular weight difunctional poly(1,2-butylene oxide) homopolymer, 15parts castor oil, 1.5 parts of 1,4 butanediol, 0.05 parts of tincatalyst and 26.3 parts of the 143 equivalent weight “liquid” MDI. Theresulting elastomer is cured at 50° C. for three days. Its tensilestrength is about 200 MPa (290 psi) and its elongation is about 440. Thewater uptake is 0.8% by weight.

Moisture Vapor Transmission Rates (MVTR) are analyzed on a MOCONPermatran-W 3/33 Water vapor permeability instrument. Standards thatapply to the instrument include ASTM F-1249, TAPPI T557 and JIS K-7129.The moisture vapor transmission rate is 1.6 g/(100 in²/day) (0.103g/m²/day).

Oxygen Transmission Rates (OTR) are analyzed on a MOCON Oxtran 2/21instrument. Standards that apply to the instrument include ASTM D-3985,ASTM F-1927, DIN 53380, JIS K-7126 and ISO CD 15105-2. The oxygentransmission rate is 80 mL/(100 in²/day) (5.16 mL/m²/day).

The moisture vapor transmission and oxygen transmission values indicatethe suitability of this elastomer for use as a secondary sealant in anIGU.

EXAMPLES 13-18

Example 13 is prepared by mixing 85 parts of a 2000 molecular weightdifunctional poly(1,2-butylene oxide) homopolymer with 15 parts ofcastor oil. To this blend are added 1.5 parts of 1,4-butanediol and 0.04parts of a tin catalyst. 50 Parts of trimethyl pentanyl diisobutyrate(TXIB plasticizer from Eastman Chemicals) are added, as are 268.5 partsof calcium carbonate particulates, 2 parts of a silane adhesionpromoter, 2 parts of an antioxidant and 5 parts by weight of a colorpaste. The resulting mixture is then combined with 24.4 parts of a 143isocyanate equivalent weight “liquid” MDI product to form a reactionmixture, which is cured as described with respect to Examples 1-6.Tensile strength, elongation and Shore A hardness are measured asbefore, with results as are indicated in Table 3 below.

Examples 14-18 are prepared and tested in the same manner, except theamount of plasticizer is varied as indicated in Table 3.

TABLE 3 Mechanical Properties Plasticizer Tensile Ex. parts by Strength,Elongation, Shore A No. weight MPa (psi) % hardness 13 50 4.00 (580) 16865 14 45 2.85 (414) 248 62 15 40 2.81 (408) 308 60 16 30 2.93 (425) 32860 17 20 2.00 (291) 260 38 18 10 1.87 (271) 277 35

When used to seal the edge of a multi-pane glass assembly, each ofExamples 13 through 18 demonstrates excellent adhesion to the glass andspacer, and forms a high quality seal.

All of these formulations have viscosities low enough to process easilyeven though many of them, especially Example 18, contain only a smallamount of plasticizer and have high filler levels.

1. A process for forming a seal between glass and a substrate,comprising: a) forming a curable reaction mixture by combiningingredients including 1) a poly(1,2-butylene oxide) polyol having ahydroxyl equivalent weight of at least 500 or a mixture of 50 to 99% byweight of a poly(1,2-butylene oxide) polyol having a hydroxyl equivalentweight of at least 500 with 1 to 50% by weight of at least one otherpolyol selected from (i) polymers and copolymers of propylene oxidehaving an equivalent weight of at least 300 and (ii) ahydroxyl-containing fat or oil, wherein component 1) has an averagenominal functionality of at least 2.2 hydroxyl groups per molecule; 2)at least one chain extender and 3) at least one organic polyisocyanate,wherein the isocyanate index is 70 to 130; b) applying the curablereaction mixture to an interface between said glass and said substrateand in contact with both said glass and said substrate; c) curing thecurable reaction mixture to form an elastomeric seal between the glassand the substrate.
 2. A process for producing an edge seal for amulti-pane glass assembly, wherein the multi-pane glass assemblycomprises at least one pair of substantially parallel glass sheets, theglass sheets of said pair being separated from each other by one or morespacers positioned between the pair of glass sheets at or near at leastone edge of the glass sheets; the process comprising a) applying acurable reaction mixture to said at least one edge of the pair of glasssheets and into contact with each of the pair of glass sheets and thespacer(s) separating said pair of glass sheets and b) curing the curablereaction mixture to form an elastomeric edge seal between the pair ofglass sheets and adherent to the spacer(s) separating the pair of glasssheets; wherein the curable reaction mixture contains 1) apoly(1,2-butylene oxide) polyol having a hydroxyl equivalent weight ofat least 500 or a mixture of 50 to 99% by weight of a poly(1,2-butyleneoxide) polyol having a hydroxyl equivalent weight of at least 500 with 1to 50% by weight of at least one other polyol selected from (i) polymersand copolymers of propylene oxide having a hydroxyl equivalent weight ofat least 300 and (ii) a hydroxyl-containing fat or oil, whereincomponent 1) has an average nominal functionality of at least 2.2hydroxyl groups per molecule; 2) at least one chain extender and 3) atleast one organic polyisocyanate, and wherein the isocyanate index is 70to
 130. 3. The process of claim 2, wherein the poly(1,2-butylene oxide)polyol preferably has a nominal functionality of 2 to 2.5 and anequivalent weight per hydroxyl group of 800 to
 1500. 4. The process ofclaim 3, wherein the poly(1,2-butylene oxide) has an average nominalhydroxyl functionality of at least 2.2 and is the only polyol having ahydroxyl equivalent weight of 200 or more in the reaction mixture. 5.(canceled)
 6. The process of claim 2 wherein component 1) is a mixtureof 70 to 95% by weight of the poly(1,2-butylene oxide) polymer and 5 to30% by weight of castor oil.
 7. The process of claim 6 whereincomponent 1) is mixture of 85 to 95% by weight of the poly(1,2-butyleneoxide) polymer and 5 to 15% by weight of castor oil.
 8. (canceled) 9.The process of claim 7 wherein the chain extender is 1,4-butane diol or1,3-propane diol.
 10. The process of claim 9, wherein the reactionmixture is devoid of a plasticizer.
 11. The process of claim 9, whereinthe reaction mixture contains 10 to 13% by weight of a plasticizer,based on the combined weight of the plasticizer and all reactivematerials provided to the reaction mixture. 12-24. (canceled)